/Engine/Source/Runtime/Engine/Classes/Kismet/KismetMathLibrary.h
Uses a simple spring model to interpolate a float from Current to Target.
static float FloatSpringInterp ( float Current, float Target, [FFloatSpringState](API\Runtime\Engine\Kismet\FFloatSpringState) & SpringState, float Stiffness, float CriticalDampingFactor, float DeltaTime, float Mass, float TargetVelocityAmount, bool bClamp, float MinValue, float MaxValue, bool bInitializeFromTarget )